#define  _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int arr[] = { 1,2,3,4,5,1,2,3,4 };
	int sz = sizeof(arr) / sizeof(arr[0]);
	int i = 0;
	int ret=0;
	for (i = 0; i < sz; i++)
	{
		ret ^= arr[i];
	}
	printf("dog=%d", ret);

	return 0;
}